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BUG: KASAN: use-after-free in disk_unblock_events+0x51/0x60 block/genhd.c:1626
Read of size 8 at addr ffff8801d4245b68 by task syz-executor5/12543

CPU: 1 PID: 12543 Comm: syz-executor5 Not tainted 4.14.0+ #176
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 disk_unblock_events+0x51/0x60 block/genhd.c:1626
 __blkdev_get+0x78d/0xf90 fs/block_dev.c:1547
 blkdev_get+0x3a1/0xad0 fs/block_dev.c:1603
 blkdev_open+0x1e4/0x270 fs/block_dev.c:1761
 do_dentry_open+0x682/0xd70 fs/open.c:752
 vfs_open+0x107/0x230 fs/open.c:866
 do_last fs/namei.c:3388 [inline]
 path_openat+0x1157/0x3530 fs/namei.c:3528
 do_filp_open+0x25b/0x3b0 fs/namei.c:3563
 do_sys_open+0x502/0x6d0 fs/open.c:1059
 SYSC_open fs/open.c:1077 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1072
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x40cbb1
RSP: 002b:00007f452e0f4710 EFLAGS: 00000293 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: cccccccccccccccd RCX: 000000000040cbb1
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 00007f452e0f47c0
RBP: 0000000000000082 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000000c R11: 0000000000000293 R12: 00000000006f6e78
R13: 00000000ffffffff R14: 00007f452e0f56d4 R15: 0000000000000000

Allocated by task 12543:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 kmem_cache_alloc_node_trace+0x150/0x760 mm/slab.c:3671
 kmalloc_node include/linux/slab.h:532 [inline]
 kzalloc_node include/linux/slab.h:678 [inline]
 __alloc_disk_node+0xb4/0x4e0 block/genhd.c:1369
 loop_add+0x44c/0xa70 drivers/block/loop.c:1795
 loop_probe+0x16d/0x1a0 drivers/block/loop.c:1902
 kobj_lookup+0x2ac/0x410 drivers/base/map.c:124
 get_gendisk+0x37/0x230 block/genhd.c:773
 __blkdev_get+0x3ea/0xf90 fs/block_dev.c:1445
 blkdev_get+0x3a1/0xad0 fs/block_dev.c:1603
 blkdev_open+0x1e4/0x270 fs/block_dev.c:1761
 do_dentry_open+0x682/0xd70 fs/open.c:752
 vfs_open+0x107/0x230 fs/open.c:866
 do_last fs/namei.c:3388 [inline]
 path_openat+0x1157/0x3530 fs/namei.c:3528
 do_filp_open+0x25b/0x3b0 fs/namei.c:3563
 do_sys_open+0x502/0x6d0 fs/open.c:1059
 SYSC_open fs/open.c:1077 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1072
 entry_SYSCALL_64_fastpath+0x1f/0x96

Freed by task 12543:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3504 [inline]
 kfree+0xca/0x250 mm/slab.c:3821
 disk_release+0x327/0x410 block/genhd.c:1218
 device_release+0x7c/0x200 drivers/base/core.c:814
 kobject_cleanup lib/kobject.c:648 [inline]
 kobject_release lib/kobject.c:677 [inline]
 kref_put include/linux/kref.h:70 [inline]
 kobject_put+0x14c/0x240 lib/kobject.c:694
 put_disk+0x23/0x30 block/genhd.c:1434
 __blkdev_get+0x6ed/0xf90 fs/block_dev.c:1540
 blkdev_get+0x3a1/0xad0 fs/block_dev.c:1603
 blkdev_open+0x1e4/0x270 fs/block_dev.c:1761
 do_dentry_open+0x682/0xd70 fs/open.c:752
 vfs_open+0x107/0x230 fs/open.c:866
 do_last fs/namei.c:3388 [inline]
 path_openat+0x1157/0x3530 fs/namei.c:3528
 do_filp_open+0x25b/0x3b0 fs/namei.c:3563
 do_sys_open+0x502/0x6d0 fs/open.c:1059
 SYSC_open fs/open.c:1077 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1072
 entry_SYSCALL_64_fastpath+0x1f/0x96

The buggy address belongs to the object at ffff8801d4245540
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1576 bytes inside of
 2048-byte region [ffff8801d4245540, ffff8801d4245d40)
The buggy address belongs to the page:
page:ffffea0007509100 count:1 mapcount:0 mapping:ffff8801d4244440 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801d4244440 0000000000000000 0000000100000003
raw: ffffea00074d0120 ffffea000766af20 ffff8801dac00c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d4245a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d4245a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d4245b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff8801d4245b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d4245c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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